Radiation is energy that travels through space and can take various forms. The main types include alpha radiation, beta radiation, and gamma radiation. Alpha radiation consists of helium nuclei and is relatively heavy, making it less penetrating. Beta radiation consists of electrons or positrons and is more penetrating than alpha particles. Gamma radiation is a form of electromagnetic radiation, similar to X-rays, and is highly penetrating. Other types include neutron radiation, which consists of free neutrons, and cosmic radiation, originating from outer space. Each type of radiation has different properties and interactions with matter.